Feeder Insects for Reptiles: Gut-Loading & Dusting Guide

Feeder Insects: Gut-Loading, Dusting, and Why Your Crickets Need Help

Most reptile keepers think feeding insects is simple. Buy crickets, drop them in the enclosure, watch the lizard eat, repeat.

The problem is that insects straight from the supplier are not a complete diet. Combined with poor lighting, an unsupplemented insect diet is one of the classic routes to metabolic bone disease and vitamin deficiencies in captive reptiles.

This guide explains what research says about the nutrition of feeder insects, how to gut-load and dust them properly, and how the common feeders compare.

← Back to complete reptile care guide

Why Feeder Insects Need Preparation

Feeder insects are a good source of protein and many nutrients, but they have well documented gaps:

• Calcium. In a detailed analysis of crickets, mealworms, superworms and waxworms raised on an enhanced diet, all four were still a poor source of calcium (Finke, 2015).
• Calcium to phosphorus ratio. A study of eight other invertebrate prey species found that in most of them the calcium to phosphorus ratio was only about 0.08 to 0.30 to 1, meaning several times more phosphorus than calcium (Oonincx and Dierenfeld, 2012).
• Vitamin A. The Merck Veterinary Manual notes that vitamin A deficiency is common in insectivorous lizards fed a diet lacking preformed vitamin A, and that many reptiles cannot use beta carotene.

The Calcium to Phosphorus Problem

The Merck Veterinary Manual describes nutritional secondary hyperparathyroidism, the most common form of metabolic bone disease, as the most common bone disease seen in reptile practice. Its listed causes include a diet with a low calcium to phosphorus ratio, vitamin D3 deficiency, lack of UVB light, and inadequate heat.

That is why insect eaters need both parts of the routine: gut-loading to improve what the insect carries, and dusting to add calcium directly. Lighting and temperature matter just as much, which is covered in our guide to metabolic bone disease in reptiles.

Gut-Loading: How to Improve Your Insects

Gut-loading means feeding your feeder insects a nutritious diet before offering them to your reptile, so their digestive tract is full of useful food when they are eaten. Many keepers gut-load for about a day or two before feeding.

What to Gut-Load With

Calcium-rich greens are a good base:

• Collard greens
• Mustard greens
• Turnip greens
• Dandelion greens
• Endive

Add variety with orange vegetables such as butternut squash, sweet potato and carrots, and some bell pepper.

Avoid relying on:

• Iceberg lettuce (mostly water)
• Spinach (its oxalates bind calcium)
• Large amounts of cabbage and other goitrogenic vegetables

Commercial gut-loads are convenient when fresh greens are not available. Repashy SuperLoad is a concentrated gut-loading powder; its listing gives a guaranteed analysis of at least 8% calcium along with other minerals and trace elements. Follow the label for how to offer it.

How Long to Gut-Load

Give insects time to eat. A common routine is to move the feeders you plan to use into a separate gut-loading container a day or two before feeding, offer fresh food, and remove anything that starts to spoil. A quick handful of greens just before feeding time does much less, because the insects have barely eaten.

Hydration Matters

Insects need moisture too, but crickets drown easily in open water bowls. Offer water through vegetables, water crystals or a gel product instead. Fluker's Cricket Quencher Calcium Fortified provides water and a little extra calcium in a form insects can't drown in (the linked listing is a large 7.5 lb bottle). Well hydrated insects also survive longer in your gut-loading container.

Calcium Dusting: The Second Half of Supplementation

Gut-loading improves the inside of the insect. Dusting coats the outside with calcium and, depending on the product, vitamins. For most insect eaters, both are part of the routine.

Calcium With or Without D3?

This depends on your UVB setup and your species, and it is worth discussing with an exotic vet.

• With good UVB: many keepers use plain calcium for most feedings and a product with D3 less often.
• With low or no UVB: the real fix is better lighting. Research on bearded dragons found that UVB raised vitamin D3 levels far more than oral D3, and that even high oral doses did not match it (Oonincx et al., 2010).
• Nocturnal species: leopard geckos deprived of vitamin D appeared to absorb enough dietary calcium passively to avoid bone disease, although geckos given low level UVB still had much higher vitamin D3 levels (summarized by Baines et al., 2016).

So plain calcium is far from useless, and more vitamin D3 is not automatically better. Vitamins A and D are fat soluble and can build up in the body, so follow the label and your vet's advice instead of adding extra.

A widely used option is Rep-Cal Phosphorus-Free Calcium with Vitamin D3 , an ultrafine calcium carbonate powder made from oyster shell.

How to Dust Properly

1. Put the insects in a bag or container with a small amount of powder.
2. Shake gently until they are lightly coated. You should still see the insect's color through a thin layer.
3. Feed them right away. Powder rubs off as insects move and groom, so dusting long before feeding wastes much of it.

Multivitamin Dusting

Calcium handles bones. A reptile multivitamin adds vitamin A, vitamin E, B vitamins and trace minerals. Because many reptiles cannot convert beta carotene, look for a product with preformed vitamin A. Use multivitamins as the label directs, usually less often than calcium, and never stack several products that contain the same vitamins.

All-in-one powders simplify this. Repashy Calcium Plus combines calcium, vitamin D3 and vitamins, and its directions say to use it with every insect feeding. Repashy also sells a low D3 version (LoD) for reptiles with regular UVB and a high D3 version (HyD) for animals with little UVB. If you use an all-in-one, don't add a separate multivitamin on top.

Feeder Insect Comparison

Every feeder insect has strengths and weaknesses. The best approach is to rotate several types and supplement them all.

1. Crickets

Pros: Widely available, inexpensive, and their fast movement triggers a strong feeding response.

Cons: Low in calcium like other feeders, noisy, smelly when they die, and hard to keep alive for long. Uneaten crickets left in the enclosure can bother a resting reptile and may nibble on it, so remove them after the meal.

Crickets are a perfectly good feeder when gut-loaded and dusted. They are simply more work to keep.

2. Dubia Roaches

Pros: Quiet, don't smell much, can't climb smooth plastic or glass, and live a long time in a simple bin, so a colony is easy to maintain.

Cons: Slower moving, so some reptiles ignore them at first; usually more expensive than crickets. They are also restricted in some places: Florida's Department of Agriculture lists pet trade feeder cockroaches, including Blaptica dubia, among prohibited non-native insects (FDACS import guidelines). Check your local rules.

3. Black Soldier Fly Larvae (BSFL)

Pros: Naturally richer in calcium than most feeders, don't smell, don't bite, and are easy to keep.

Cons: Their calcium is not as available as it looks. In a four month trial with 24 leopard geckos, only about 43% of the calcium in BSFL was digested, because the calcium-rich outer skin often passed through intact, and blood tests hinted at possible calcium deficits over time (Boykin et al., 2020). The authors concluded that more research is needed before BSFL can be considered an adequate calcium source without supplements.

BSFL are a useful part of a varied diet, but they don't replace dusting. Fluker's Live Black Soldier Fly Larvae come as 500 small live larvae, gut-loaded by Fluker's before shipping according to the listing. Follow the supplier's storage instructions so they stay alive.

4. Mealworms

Pros: Easy to store, inexpensive, and they stay put in a feeding dish.

Cons: Low in calcium and relatively high in fat. Fine as part of a rotation for species that accept them, especially when gut-loaded and dusted.

5. Superworms

Pros: Larger and more active than mealworms, which tempts picky eaters.

Cons: Fatty, low in calcium, and they can give a firm bite with their mandibles. Best as an occasional item for larger reptiles.

6. Hornworms

Pros: Soft bodied, very juicy, and popular with many lizards, which makes them useful for picky or dehydrated animals.

Cons: Expensive and fast growing, so they need to be used quickly. They are not a complete diet on their own.

7. Waxworms

Pros: Very appealing to most reptiles.

Cons: Very high in fat. Fed often, they can lead to obesity and some reptiles start refusing other food. Keep them as a rare treat or a tool to tempt a sick animal to eat, with your vet's guidance.

Common Feeder Insect Mistakes

1. Feeding straight from the supplier's container. Gut-load first.
2. Using only one feeder type. Rotate two or three types to cover more nutritional gaps.
3. Over-supplementing. Stacking several vitamin products or using D3 at every feeding without reason can do harm. Follow labels and your vet.
4. Feeding insects that are too large. A common rule of thumb is no larger than the space between your reptile's eyes.
5. Leaving live crickets in the enclosure. Remove uneaten insects after the meal.
6. Relying on supplements instead of UVB. For basking species, supplements support good lighting; they don't replace it.

Which Feeders for Which Species

• Bearded dragons: dubia roaches, crickets, BSFL and hornworms, plus a large share of vegetables as they mature.
• Leopard geckos: crickets, dubia roaches, mealworms and BSFL, with waxworms as a rare treat.
• Blue-tongued skinks: omnivores that take insects and snails alongside vegetables and other foods.
• Chameleons: a varied mix of flying and crawling insects such as crickets, roaches, hornworms and silkworms.
• Crested geckos: mainly a complete commercial diet, with insects offered as a supplement.

Requirements vary by species and age, so ask an exotic vet to review your feeding plan. For a species that lives almost entirely on insects, see our leopard gecko care guide.

Final Thoughts: Insects Are Only as Good as You Make Them

Feeder insects are a good base for an insect eater's diet, but on their own they are low in calcium and often short on vitamin A. Gut-load them, dust them with the right product for your setup, rotate several species, and give your reptile proper heat and UVB. That combination is what keeps bones strong and growth steady.

← Back to complete reptile care guide

Resources & References

• Finke MD. (2015). Complete nutrient content of four species of commercially available feeder insects fed enhanced diets during growth. Zoo Biology. PubMed 26366856
• Oonincx DGAB, Dierenfeld ES. (2012). An investigation into the chemical composition of alternative invertebrate prey. Zoo Biology. PubMed 21442652
• Boykin KL, et al. (2020). Digestibility of black soldier fly larvae (Hermetia illucens) fed to leopard geckos (Eublepharis macularius). PLoS One. PubMed 32392254
• Oonincx DGAB, et al. (2010). Effects of vitamin D3 supplementation and UVb exposure on the growth and plasma concentration of vitamin D3 metabolites in juvenile bearded dragons. PubMed 20206712
• Baines FM, et al. (2016). How much UV-B does my reptile need? The UV-Tool. Journal of Zoo and Aquarium Research. jzar.org
• Merck Veterinary Manual: Nutritional, Metabolic, and Endocrine Diseases of Reptiles
• Florida Department of Agriculture and Consumer Services: Guidelines for Importing Exotic Arthropods